<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>Document</title>
	<script type="text/javascript">
        window.onload = function(){
        	var oBtn1 = document.getElementById('btn1');
            var oBtn2 = document.getElementById('btn2');
            var oBtn3 = document.getElementById('btn3');

            var oDiv = document.getElementById('div1');
            var aCh = oDiv.getElementsByTagName('input');

            //全选
            oBtn1.onclick = function(){
                for(var i=0;i<aCh.length;i++){
                	aCh[i].checked = true;     //checked html怎么写  js就怎么写
                }
            }

            //不选
            oBtn2.onclick = function(){
                for(var i=0;i<aCh.length;i++){
                	aCh[i].checked = false;
                }
            }

            //反选
            oBtn3.onclick = function(){
                for(var i=0;i<aCh.length;i++){
                	if(aCh[i].checked == true){
                        aCh[i].checked = false;
                	}else{
                		aCh[i].checked = true;
                	}
                	
                }
            }
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</head>
<body>

    <input id="btn1" type="button" value="全选" />
    <input id="btn2" type="button" value="不选" />
    <input id="btn3" type="button" value="反选" />
    <div id="div1">
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    	<input type="checkbox" /><br />
    </div>
	
</body>
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